The crucial role of mitochondrial regulation in adaptive aluminium resistance in Rhodotorula glutinis.
Rhodotorula glutinis IFO1125 was found to acquire increased aluminium (Al) resistance from 50 microM to more than 5 mM by repetitive culturing with stepwise increases in Al concentration at pH 4.0. To investigate the mechanism underlying this novel phenomenon, wild-type and Al-resistant cells were compared. Neither cell type accumulated the free form of Al (Al(3+)) added to the medium. Transmission electron microscopic analyses revealed a greater number of mitochondria in resistant cells. The formation of small mitochondria with simplified cristae structures was observed in the wild-type strain grown in the presence of Al and in resistant cells grown in the absence of Al. Addition of Al to cells resulted in high mitochondrial membrane potential and concomitant generation of reactive oxygen species (ROS). Exposure to Al also resulted in elevated levels of oxidized proteins and oxidized lipids. Addition of the antioxidants alpha-tocopherol and ascorbic acid alleviated the Al toxicity, suggesting that ROS generation is the main cause of Al toxicity. Differential display analysis indicated upregulation of mitochondrial genes in the resistant cells. Resistant cells were found to have 2.5- to 3-fold more mitochondrial DNA (mtDNA) than the wild-type strain. Analysis of tricarboxylic acid cycle and respiratory-chain enzyme activities in wild-type and resistant cells revealed significantly reduced cytochrome c oxidase activity and resultant high ROS production in the latter cells. Taken together, these data suggest that the adaptive increased resistance to Al stress in resistant cells resulted from an increased number of mitochondria and increased mtDNA content, as a compensatory response to reduced respiratory activity caused by a deficiency in complex IV function.
Tani
Akio
A
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
Inoue
Chiemi
C
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
Tanaka
Yoko
Y
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
Yamamoto
Yoko
Y
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
Kondo
Hideki
H
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
Hiradate
Syuntaro
S
National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaragi 305-8604, Japan.
Kimbara
Kazuhide
K
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
Kawai
Fusako
F
Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.
D000535:Aluminum / Q000378:metabolism* / Q000494:pharmacology; D002952:Citric Acid Cycle; D004272:DNA, Mitochondrial / Q000235:genetics; D004351:Drug Resistance; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017382:Reactive Oxygen Species / Q000378:metabolism; D012248:Rhodotorula / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D000535:Aluminum